INTRODUCTION

The wastewater from industries varies so greatly in both flow and pollutional strength.

So, it is impossible to assign fixed values to their constituents. In general, industrial

wastewaters may contain suspended, colloidal and dissolved (mineral and organic) solids. In

addition, they may be either excessively acid or alkaline and may contain high or low

concentrations of coloured matter. These wastes may contain inert, organic or toxic materials

and possibly pathogenic bacteria. These wastes may be discharged into the sewer system

provided they have no adverse effect on treatment efficiency or undesirable effects on the

sewer system. It may be necessary to pre-treat the wastes prior to release to the municipal

system or it is necessary to a fully treatment when the wastes will be discharged directly to

surface or ground waters.

Several industries discharge heavy metals, it can be seen that of all of the heavy

metals such as zinc, manganese, aluminium, iron, copper, chromium, lead, nickel, cadmium

and other metals. Chromium is the most widely used and discharged to the environment from

different sources. As shown in Figure 1.1, many of the pollutants entering aquatic ecosystems

such as mercury lead, manganese, pesticides, and herbicides etc are very toxic to living

organisms. They can lower reproductive success, prevent proper growth and development,

and even cause death. The heavy metal ions are stable and persistent environmental

contaminants since they cannot be degraded and destroyed.

Fig. 1.1 Discharge of untreated industrial wastewater to a river

However, much more toxic are cadmium, lead and mercury that is most dangerous to

living organisms. These have a tremendous affinity for sulphur and disrupt enzyme function

by forming bonds with sulphur groups in enzymes. Protein carboxylic acid (-CO2H) and

amino (-NH2) groups are also chemically bound by heavy metals. Heavy metal ions bind to

cell membranes, hindering transport processes through the cell wall. Heavy metals may also

precipitate phosphate bio-compounds or catalyse their decomposition. Heavy metals found in

major industries shown in Table 1.1.

Table 1.1: Heavy Metals in Major Industries

The treatment and removal of heavy metals have drawn considerable attention

because of their association with various health problems. Although metals such as Zn and

Cu are essential nutrients at low levels (but are toxic at higher concentration), other such as

Pb could bring severe physiological or neurological consequences even in small amounts.

This treatment can be done by using jar test method where it measures the effect of

coagulation, flocculation, and sedimentation on turbidity. It is a reliable method to determine

the proper mixing of chemical dosage and suitable condition for coagulation of water to

remove colour and turbidity.

Basically, In Malaysia, the industrial wastewater discharge is regulated by Sewage

and Industrial Effluent Regulations, 1979 (EQA 1974 (2002)). Various waste constituents

may have to be removed or reduced to meet standard discharge limits before being released

to the receiving streams. Currently, most of the industries in Malaysia treat their wastewater

in order to meet the Standard B discharge limits. The Standard B discharge limits for lead,

zinc and copper, and iron are 0.5 mg/L, 2.0 mg/L and 1.0 mg/L, respectively. However, the

Department of Environment of Malaysia may raise the industrial discharge limits to become

more stringent, especially in the heavy metal concentrations, for protection of the

environment from serious pollution in the future. Considerable investment and research have

been focused on the improvement of many well-established technologies.

Heavy metals are known as soluble ions that common contaminants of industrial

wastewaters. Because of their toxicity they are typically removed prior to wastewater

discharge. Therefore, the design of efficient and cost effective heavy metals wastewater

removal methods is therefore an important technological issue. The system under study

consists in a jar test apparatus for the removal of heavy metals from wastewater through

coagulation and flocculation. Jar testing is a method of simulating a full scale water treatment

process, providing system operators a reasonable idea of the way a treatment chemical will

behave and operate with a particular type of raw water. Because it mimics full-scale

operation, system operators can use jar testing to help determine which treatment chemical

will work best with their system’s raw water. Jar testing entails adjusting the amount of

treatment chemicals and the sequence in which they are added to samples of raw water held

in jars or beakers. The sample is then stirred so that the formation, development, and

settlement of floc can be watched just as it would be in the full scale treatment plant. (Floc

forms when treatment chemicals react with material in the raw water and clump together.)

The operator then performs a series of tests to compare the effects of different amounts of

flocculation agents at different pH values to determine the right size floc for a particular plant

OBJECTIVES

The main purpose of the jar test is to study relationship of heavy metal removal and pH. The

aim of the experiment is to measure the properties of wastewater by its turbidity, heavy

metals (Iron) content by using jar test at different pH.

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Maessen, O, Freedman, B. and McCurdy, R. (1985). Metal Mobilization in Home Well Water

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